Your link is to an "old technology" diode-type battery isolator. Looks something like this--
Diode isolators work, and they get used a lot in boats and RV's etc., but they need all those cooling fins because diode-type isolators get hot. Heat=bad, IMO. Also, diode-type isolators consume a certain amount of juice so that your bike is gonna run at less than full voltage and the two batteries never really reach full charge.
A more "new technology" isolator is a voltage sensing relay sometimes called an ACR (Automatic Charging Relay). Consumes only milli-amps of power and produces no heat. Something like this--
Here's a cool diagram from the Blue Sea website showing the difference in how they get wired up--
Seems like the ACR would work a lot better on a bike. BTW, that ACR shown above only costs $85 - link
If you want to do something like this, you need to make sure that the power for the aux circuits that you plan to use when the bike is not running comes from the 2nd battery, not from your main battery. If you have an aux fuse panel that is triggered by a switched circuit (fuse panel turns on only when the bike is running), then the aux circuits that you want to run when the bike is turned off are going to have to be connected directly to the 2nd battery, or install a 2nd fuse panel powered by the 2nd battery with a trigger switch that also goes directly to the 2nd battery.
There's a lot of good basic info about isolators at the Yandina website
. Yandina is a West Marine spin-off located in South Carolina.